In Type III construction, which roof feature can spread fire if not properly fire-stopped?

In Type III construction, which roof feature can spread fire if not properly fire-stopped?

• A. Nonoperating windows or other openings
• B. Open web joists supporting metal roof decks
• C. Void spaces inside wooden channels in the roof
• D. Foam insulation sandwiched between sheets of plywood

Answer: (C)

In Type III construction, the roof framing is primarily wood, and the assembly often contains hidden voids and channels between members. Fire stopping (fire blocking) is used to interrupt flame paths through those concealed spaces. When void spaces inside wooden channels in the roof aren’t properly fire-stopped, flames and hot gases can travel through those hidden paths, allowing the fire to spread rapidly from one part of the roof or attic to another. This concealed spread is a major risk because it occurs out of sight and can undermine firefighting efforts by preheating and igniting adjacent wood members farther from the visible flames. Other features like openings and joist configurations can contribute to spread in different ways, but the specific risk described here is the movement of fire through the void spaces inside wooden roof channels, which is why that option is the best fit.

In Type III construction, the roof framing is primarily wood, and the assembly often contains hidden voids and channels between members. Fire stopping (fire blocking) is used to interrupt flame paths through those concealed spaces. When void spaces inside wooden channels in the roof aren’t properly fire-stopped, flames and hot gases can travel through those hidden paths, allowing the fire to spread rapidly from one part of the roof or attic to another. This concealed spread is a major risk because it occurs out of sight and can undermine firefighting efforts by preheating and igniting adjacent wood members farther from the visible flames.

Other features like openings and joist configurations can contribute to spread in different ways, but the specific risk described here is the movement of fire through the void spaces inside wooden roof channels, which is why that option is the best fit.